Experts Review Wetlands in Climate Change Context

Jul 23, 2008

Scientists are convening in Brazil this week (July 21-25) amid growing concern that evaporation and ongoing destruction of wetlands, which hold a volume of carbon similar to that in the atmosphere today, could cause them to exhale greenhouse gases.

Meeting in the city of Cuiaba on the edge of South America's vast Pantanal, the largest wetland of its kind, some 700 experts from 28 nations at the 8th INTECOL International Wetlands Conference will prescribe measures needed to better understand and manage these ecosystems and slow their decline and loss.

Warming world temperatures are speeding both rates of decomposition of trapped organic material and evaporation, while threatening critical sources of wetlands recharge by melting glaciers and reducing precipitation.

Covering just 6 percent of Earth's land surface, wetlands store 10 to 20 percent of its terrestrial carbon. Wetlands slow the decay of organic material trapped and locked away over the ages in low oxygen conditions. Wetlands include marshes, peat bogs, swamps, river deltas, mangroves, tundra, lagoons, and river floodplains.

These waterlogged (either seasonally or year-round) areas contain an estimated 771 gigatons (771 billion tons) of greenhouse gases -- both carbon dioxide (CO2) and more potent methane -- an amount in CO2-equivalent comparable to the carbon content of today's atmosphere.

"Humanity in many parts of the world needs a wake-up call to fully appreciate the vital environmental, social, and economic services wetlands provide – absorbing and holding carbon, moderating water levels, supporting biodiversity, and countless others," said conference co-chair Paulo Teixeira, coordinator of the Cuiaba-based Pantanal Regional Environmental Program, a joint effort of the United Nations University and Brazil's Federal University of Mato Grasso (UFMT), which is hosting the event.

If the decline of wetlands continues through human and climate change-related causes, scientists fear the release of carbon from these traditional sinks could compound the global warming problem significantly, says Professor Paulo Speller, Rector of UFMT. Drained tropical swamp forests release an estimated 40 tons of carbon per hectare per year. Drained peat bogs release some 2.5 to 10 tons of carbon per hectare per year.

German expert Wolfgang Junk says the impact of climate change on wetlands is small so far compared to the damage caused by poor management at the local level.

"Lessening the stress on wetlands caused by pollution and other human assaults will improve their resiliency and represents an important climate change adaptation strategy," he says. "Wetland rehabilitation, meanwhile, represents a viable alternative to artificial flood control and dredging efforts that may be needed to cope with the larger, more frequent floods predicted in a hotter world."

Professor Junk, of the Max-Planck-Institute for Evolutionary Biology, notes that maintenance of wetlands is much cheaper than rehabilitation and that poorer countries will have fewer means to rehabilitate their wetlands to cope with climate change. Wetland-friendly development alternatives must be elaborated in developing countries, therefore, to minimize losses of their many benefits, he says.

He notes too that while pressure on wetlands in poorer countries has risen dramatically in recent years, they have not suffered nearly as much damage as those in the developed world.

Some 60 percent of wetlands worldwide -- and up to 90 percent in Europe -- have been destroyed in the past 100 years, principally due to drainage for agriculture but also through pollution, dams, canals, groundwater pumping, urban development, and peat extraction.

Conference organizers say efficient protection of wetlands requires complex, long-term management plans that cover their entire catchment areas, often involving agreements between states or countries. These agreements need to cover activities that affect wetlands both directly and indirectly, such as the use of water and soils, development, waste treatment and disposal, but also harmonization of environmental legislation for protection of wetlands and all that lives in them.